In industrial food processes it is common that a solid-liquid mixture needs to be separated into its liquid component and its solid component. There are polymer flocculants available currently to perform this separation. However, useful materials in the liquid component of such separations are typically not harvested because of concern that the liquid component is contaminated with polymer flocculants. This concern about contamination has led to much valuable material being discarded.
For example, in the recovery of sugar, cationic flocculants are used to effect solid-liquid separation. The liquid portion still contains recoverable sugar, but this sugar is not recovered, because the liquid may have been contaminated with flocculant. In order not to waste this recoverable sugar, there is a recognized need to develop either an environmentally safe (for food use) polymer or a detectable polymer. Of these two routes, it was decided to pursue a detectable polymer as a solution.
In pursuing a solution it was noted that immunoassay detection technology was already in existence for the coagulant polymers epichlorohydrin dimethylamine (hereinafter "epi-DMA") and polydiallyldiammonium chloride (hereinafter "polyDADMAC"). Epi-DMA is available as Nalco.RTM.8105 from Nalco Chemical Company, One Nalco Center, Naperville, Ill. 60563 ((630) 305-1000). PolyDADMAC is available as Nalco.RTM.8103 from Nalco Chemical Company. Although these polymers are detectable, it was found that these polymers did not have a sufficient molecular weight to act as flocculants.
Building on the use of immunoassay as the detection method of choice, a 30/70 mole percent acrylamide/DADMAC copolymer (which is available from Nalco Chemical Company as Nalco.RTM.7527) was tested in the sugar application. This polymer has molecular weights greater than the coagulants, but not as high as a flocculant. Because of the high concentration of DADMAC, this polymer was detectable using the Nalco.RTM.8103 (polyDADMAC) immunoassay test kit. A field trial was run, which was a failure. Although detectable in the liquid component, the polymer did not form strong robust flocs and the solids were not effectively dewatered. This failure can be related to both charge and molecular weight. It was known that DADMAC monomer does not polymerize to high molecular weights, so copolymers containing DADMAC are more like coagulants than flocculants.
Based on the above results, the criteria for a polymer flocculant to be successful in this application were determined to be as follows:
1) polymer flocculant must form effective flocs that will effect solid-liquid separation (i.e. getting the correct charge), PA1 2) the floc strength must be sufficient to withstand the shear of the dewatering process (i.e. having sufficient molecular weight), and PA1 3) the polymer must be detectable (by immunoassay) to quantify the level of polymer in the liquid. PA1 a) adding a cationic flocculant polymer to a liquid component of an industrial food process which causes the formation of flocculated particles, wherein said cationic flocculant polymer comprises a first monomer component, which is nonionic; PA1 a second monomer component, which is cationic; and PA1 a third monomer component which is diallyl dimethylammonium chloride; PA1 b) separating said flocculated particles from said liquid component; and PA1 c) determining the concentration of said cationic flocculant polymer in the liquid; wherein the step of determining the concentration of the cationic flocculant polymer further comprises: PA1 a first monomer component, which is nonionic; PA1 a second monomer component, which is cationic; and PA1 a third monomer component which is diallyl dimethylammonium chloride. PA1 from about 5 to about 80 mole percent of the first monomer component, which is nonionic; PA1 from about 5 to about 90 mole percent of the second monomer component, which is cationic; and PA1 from about 3 to about 30 mole percent of the third monomer component, which is diallyldimethylammonium chloride. PA1 a) adding a cationic flocculant polymer to a liquid component of an industrial process which causes the formation of flocculated particles, wherein said cationic flocculant polymer comprises a first monomer component, which is nonionic; PA1 b) separating said flocculated particles from said liquid component; and PA1 c) determining the concentration of said cationic flocculant polymer in the liquid; wherein the step of determining the concentration of the cationic flocculant polymer further comprises: